[oliverrice]

> How do you mock it? How do you test it?

Stripe and Firebase both offer test endpoints for their services. The foreign data wrappers for each allow subbing in a user defined endpoint in their `options` so thats how I'd recommend testing the two that have released. Some of the pre-release integrations can be spun up locally in docker e.g. clickhouse. The FDWs for those similarly take an arbitrary connection string making it pretty straightforward to write tests. Here's an example from the repo https://github.com/supabase/wrappers/blob/5fac8afb62e6e8362b...

> Add custom logic?

Views!

> tasks that the database is not designed to do

The C API for foreign data wrappers is baked right into Postgres proper. They've been around since 2013 and are pretty battle hardened at this point. Supabase Wrappers exposes that API in rust so users can write FDWs without worrying about accidentally tanking the Postgres process. Its more about making a great Postgres feature more accessible than tricking the database into doing anything new.

[kiwicopple]

another possibility for application developers - mocking can be done at the "application" level. For example, using something like Jest, or Supabase can build mocking into client libs.

I'm not clear how mocking in the middleware is materially different from this approach (except perhaps you are testing network connectivity too).